Problem with xdm....help

Hello friends....
I installed Debian linux 3.0 and I have a problem with display manager.. My system is booting in GUI mode well. When I give user name and password then it is comming desktop enviroment for a moment and it is comming login window to login again.....
I receive the following error in a little window at right bottom of screen....

april 15 12:00:00 (none) PAM_linux[240]: (xdm) Session closed for user root
april 15 12:00:00 (none) modprobe : can't locate module char-major-13
april 15 12:00:00 (none) kernel : neighbour table overflow

Please give your comments......................thanks

I haven't seen this problem before, but here's some general troubleshooting advice.
1. Type Ctrl+Alt+F5. This should get you to a text mode login screen.
2. Login as root. Type "init 3" at the prompt.
3. Wait for a text mode login screen and login as root again.
4. Run "startx".
5. See if you get the same error.

This should be your general procedure for troubleshooting any graphical login problems. However, in your case, I'm almost certain that you'll get the same error even after typing startx and that X will fail to start. A missing module might mean:
1. Installation wasn't done properly.
2. Your downloaded image is corrupted.
3. The CD didn't burn properly and thus has a corrupted filesystem.

Solutions:
1. Download the md5 checksum of the ISO and check it against your downloaded ISO file.
2. If the md5 checksum tells you that your file is fine, burn it to another CD and reinstall Linux.

Cheers,
cgkanchi